Control of machine components



Nov. 30, 1965 J. L. GOOD CONTROL OF MACHINE COMPONENTS 2 Sheets-Sheet 1Filed March 29, 1962 PATENT AG NT Nov. 30, 1965 J. GOOD CONTROL OFMACHINE COMPONENTS 2 SheetsSheet 2 Filed March 29, 1962 FIG.3

INVENTOR. JAMES L. GOOD BY wauwmrmw PATENT A65 NT FIG.4

United States Patent 3,220,377 CQNTROL 0F MACNE COMPONENTS James L.Good, Oakland, Md, assignor to West Virginia Pulp and Paper Company, NewYork, N.Y., a corporation of Delaware Fiied Mar. 29, 1962, Ser. No.183,525 8 Claims. (Cl. 118-8) This invention relates generally to amethod of and apparatus for removing machine components from a travelingweb during the passage of a void or similar defect to prevent paper webbreaks and more specifically to a method of and apparatus for removingcoating components from a paper web during the travel of a defecttherethrough, whereby the defect in the paper web will not be furtherenlarged by the coating components.

On conventional paper machines, the paper web traveling from the formingsection, such as a fourdrinier, can be damaged by various machinecomponents. The damages may be in the form of voids, creases, and tearsthat are not always large enough to break the paper web. However, thedefects provide a weakened area in the paper web which can be enlargedby machine components that subject the paper web to a substantialpressure or drag.

Those familiar with the art of coating a paper web are well aware thatblade coaters are a continual cause of defect enlargement that resultsin paper web breaks. The blades employed to meter the coating subjectsthe paper web to considerable pressure and drag just after the paper web.has been wetted and thereby weakened by the coating application.

Those familiar with blade coating are well aware that better coatingweight control, lighter coating weights, and improved coating qualityare possible with an increase in the coating blade angle. Blade angle asused in the description refers to the acute angle at which the bladeapproaches the surface of the paper Web. In the past, this fact has beencompromised because an increase in blade angle also increases theprobability of defects in the paper web being amplified, sometimes tothe extent of breaking the paper web, as the defect passes under theblade edge. With the invention, the advantages of the higher blade anglecan be realized without increasing the machine down-time resulting froma paper web break in the coater.

It should not be interpreted that paper web defects will only beamplified in the blade coaters if the blade angle is large. It is to beunderstood that the probability of enlargement increases with anincrease in the blade angle. Therefore, the invention is applicable forall blade coating operation regardless of the blade angle.

A control system designed according to the invention will automaticallydetect a defect in the paper web and interrupt the coating operationsduring the passage of the defect therethrough. Briefly described, theblade and applicator roll of the blade coaters are incorporated into acontrol circuit that automatically senses the defect prior to thecoaters, times the travel of the defect through the paper machine,causes removal of coater components during the passage of the defecttherethrough, and causes replacement of the coater components after thepassage of the defect therethrough.

The removal of the coating components stops the transfer of coating tothe paper web which alters the tension by drastically reducing themoisture content. In some paper machines, the coaters have paper webtension control systems that provide enough control during normaloperations. However, especially in the lighter weight paper webs, thesudden drastic change in paper Web tension resulting from coater removalcannot be corrected ICC by the tension control systems quickly enough toprevent breakage of the paper web. In such cases, supplemental tensioncorrection controls should be included in the basic control circuitwhich anticipate the forthcoming need for tension correction and beginto correct the. instant the coater components are removed. This is to becontrasted with conventional tension control systems that must sense achange in the paper web tension before beginning correction.

In the past, it was found advantageous in roll coaters to remove thecoating applicator rolls from the backing rolls to prevent the transferof coating during the absence of the paper web. When the paper web wasbroken prior to the roll coaters, coating material carried on thesurface of the applicator roll was in direct contact with the surface ofthe backing roll. Coating was transferred from the applicator roll tothe backing roll where it either transferred to the back side of therestored paper web or formed an irregular surface on the backing roll.In either case, the result was undesirable.

It should be realized that the invention is dealing with distinctlydifferent problems. In roll coaters, the problem has been to prevent thetransfer of the coating onto the backing roll during the absence of thepaper web. In blade coaters, the problem is primarily to preventexpansion of a defect in the paper Web by the blade which could resultin a break and necessitate a machine shutdown to clear the coaters.

Since the blade controls the amount of coating that is retained on thepaper web, its removal results in the absence of coater metering. Thesurplus coating would be transferred to the paper web and would travelon the paper web to the dryer rolls immediately following the coaterwhere the coating would adhere to the dryer roll surfaces. To avoidcoating transfer, the applicator roll of the blade coater must beremoved from the paper web before the operation of the blade ceases. Theprocedure also prevents the transfer of coating through the defect tothe backing roll. Removing the applicator roll does not prevent paperweb breaks which result from the coating blade drag and pressure, butprevents coating transfer.

A common occurrence in blade coaters once the paper Web has broken isthat since the paper web is still being fed from the forming section, itis fed either into the coating pan or is wrapped around the backing rollof the coater. Either case requires considerable time to clean thecoaters of the entangled paper web.

On a broader scale, defects in the form of voids, local caliper (lumps)differences, moisture differences, creases, edge cracks, and tears canbe detected before they pass through any machine component that exertsconsiderable exterior force on the paper web such as pressure or drag.For example, it is well known that wet spots in the paper web tend toadhere to the surfaces of the rolls of a calender stack and arefrequently torn from the paper web by the adhering action. The void,once created, presents a weakened area in the paper web that is apossible source of breaks. An anticipatory method of controlling thecalender rolls according to this invention could be employed to overcomethe adhering tendencies by sensing the wet spots and unloading thecalender stack during the passage therethrough. Regardless of thecomponent controlled, it will become evident in the followingdescription that similar methods could be employed. The control ofcalenders and size presses to mention a few are all within the scope ofthis invention.

It should become evident, therefore, that this invention is concernedprimarily with a means for preventing the amplification of paper webdefects in the blade coaters of paper machines.

In addition, this invention allows an increase in blade angle whichresults in better coating weight control Without increasing the papermachine down-time.

Further, paper machines manufacturing very lightweight paper Webs canhave a protected coater system without having tension control problems.

Still further, machine down-time resulting from paper web breaks,regardless of the blade angle, is reduced.

Also, a fully automatic control is obtained that stops the coatingduring the passage of the paper web defects and starts the coating afterthe passage of the paper web defects.

Further advantages will hereinafter more fully appear in connection witha detailed description of the drawings in which:

FIG. 1 is a schematic side elevational view of a coater section of apaper machine.

FIG. 2 is a schematic circuit diagram of a control system according tothe present invention for the coater of FIG. 1.

FIG. 3 is an enlarged fragmentary schematic circuit diagram of anotherembodiment of a control system according to the present invention.

FIG. 4 is an enlarged fragmentary schematic circuit diagram of anothercontrol system according to the present invention employing asupplementary tension control.

Referring to FIG. 1 of the drawings, the paper web is fed into the firstcoater, broadly indicated by the reference 11, from the forming sectionof the paper machine (not shown). The paper web 10 contacts a defectdetector 12 as the paper web passes over the idler roll 13. From theidler roll, the paper web travels around another roll 14 and around thetension roll 15 and through the nip created by the applicator roll 16and the backing roll 17 Where the coating is applied to one side of thepaper web. The coating is metered by the blade 18, and in thisparticular embodiment, the paper web then travels around three dryerrolls 19 and enters into the second coater (broadly indicated byreference 20). Prior to passage through the second coater, the paper webengages a second tension roll 21. The paper web travels through the nipcreated by the applicator roll 22 and the backing roll 23 where coatingis applied to the opposite side of the paper web. The coating is thenmetered by the blade 24 of the second coater. The second coater also hasthree dryer rolls 25. The paper web leaves the second coater and passesthrough the machine to a winder stand which is not shown. FIG. 1 is anexample of a coater which applies a single coat to both sides of thepaper web, and forms no particular part of the invention.

Referring to FIG. 2, notice that the defect detector 12 of FIG, 1 isschematically represented by a normally open solenoid operated singlepole-single throw switch. The switch is intended to be illustrative ofthe action of the defect detector and obviously does not represent thetrue situation. Suitable void detectors are commercially available, suchas those made by Curtiss-Wright. As will become apparent in thefollowing discussion, the defect detector is energized by the passage ofa defect usually in the form of a void. The defect energizes thedetector, closing the single pole-single throw switch.

The applicator roll 16 of the first coater is positioned by the springreturn cylinder 26. The blade 18 of the first coater is positioned bythe spring return cylinder 27. In the second coater 20, the applicatorroll 22 is positioned by a similar spring return cylinder 28 and theblade 24 by a similar cylinder 29. The applicator roll cylinder 25 ofthe first coater has a fluid loaded end controlled by a two-way springreturn valve 30. The blade cylinder 27 of the first coater is controlledby a similar valve 31. In the second coater, the applicator rollcylinder 28 is likewise controlled by a similar valve 32 as is the bladecylinder 29 controlled by the valve 33. One side of the solenoidscontrolling the two-way valves 30, 31, 32, and 33 are joined to a commonwire 34 by the fed wires 35 and 36. Common Wire 34 pro vides a voltagepotential of, for example, volts with the main Wire 37. The other sideof the solenoids are individually connected to the main Wire 37 throughswitches. The single pole-single throw switch 38 connects through wire39, the solenoid of the two-way spring return valve 31 and, in a similarmanner, the switch 40 through wire 41 connects the solenoid of thetwo-way spring return valve 30. In the second coater, switches 42 and 43through wires 44 and 45 connect the solenoids of the two-way springreturn valve 33 and the two-way spring return valve 32, respectively. Itis to be understood that when any of the switches 38, 4t 42, or 43 areclosed, the corresponding two-way spring return valves will be forcedinto a position which will exhaust the fluid end of the correspondingcylinders. The exhaust will bring about the removal from the paper webof the components positioned by the cylinders. The switches should beconveniently centralized where manual control by the machine operatorsis easily accomplished.

Up to this point, the circuitry is intended to be illustrative of astandard manual control circuit. Many modifications by those familiarwith the art are possible that could still be used in connection withthe invention as described in detail in the following description.

Referring again to FIG. 2, a drum timer 46 is composed of 5 contactstrips 47, 43, 45 5d, and 51. Each of these contact strips has acorresponding pickup shoe 52, 53, 54, 55, and 56. The drum of the drumtimer is driven by the motor 57. Notice that the motor 57 is joineddirectly to the common wire 34 and indirectly to the main wire 37through the defect detector 12 by wires 5-3 and 59. The contact strips47 through 51 are connected to the main wire 37 through the wires 59 and60. Wire 51 connects the pickup shoe 52 to the pole of the motor 57 thatis also connected by wire 58 to the defect detector 12. Pickup shoes 53through 56 are individually connected to one end of the solenoids of thetwo-way spring return valves 30, 31, 32, and 33 through wires 62 through65, respectively. The drum timer and the defect detector circuitscombine with the manual control circuit to form a novel system wherebythe passage of paper web defects will not be amplified in the coatingsection of the paper machine. The two following illustrative examplesexplain the operating procedure of the system as shown in FIG. 2. Thefirst of these examples will deal with the normal operation of themanual control circuit by the machine operators. The second illustrativeexample will deal with the operation of the control circuit when thecoaters are in operation and the defect detector senses a defect in thepaper Web.

Assume that the paper web is traveling through the coaters shown in FIG.1, and that the applicator rolls 16 and 22, and the blades 18 and 24 arenot contacting the paper web. Proper paper web tensions are throughoutthe paper machine and coating operations are to begin. The singlepole-single throw manual control switches 38, 40, 42, and 43 which arenormally located on a control console in a position relatively close tothe coaters are in a closed position. Therefore, from FIG. 2, a voltagepotential is applied across the solenoids of the two-way spring returnvalves 3t 31, 32, and 33. To begin coating, the machine operator opensswitch 38 which in turn will deactivate the solenoid of the valve 31 andallow the spring to move the controller 31 into the position as shown inFIG. 2 whereby fluid will be admitted into the fluid end of the cylinder27. The blade 18 will be forced against the backing roll 17 by the fluidpressure. Next, the operator will open switch 4 0 which will deactivatethe solenoid on the valve 30. The movement caused by the spring of thevalve 359 will direct fluid into the cylinder 25 which will force theapplicator roll 16 against the backing roll 17. It is to be understoodthat the angle of the blade 18 is pre-set before the startup operationas would be obvious to those skilled in the art. Therefore, by placingthe blade 18 and the applicator roll 16 against the paper web, thecoating of one side of the web has been initiated. It is important tonotice that the blade 18 was placed against the web prior to theapplicator roll 16. Failure to apply the components in this sequencewould result in a transfer of excess coating on the paper web. Excesscoating could cause a paper web break because of the excess moisture, orcould be transferred to the dryer rolls 19 of the first coater. Eithereffect is detrimental and would require machine down-time to correct. Asimilar procedure is carried out to begin the coating operation of thesecond coater. The operator opens switch 42 which deactivates thesolenoid of the two-way spring return valve 33. Fluid will be forcedinto the cylinder 29 of the blade 24 which will force the blade againstthe paper web. Next, the operator will open switch 43 which willdeactivate the solenoid of the two-way spring return valve 32, thusadmitting fluid under pressure into the cylinder 28 which will in turnforce the applicator roll 22 against the backing roll 23. Notice thatthe blade 24 is placed against the paper web prior to the applicatorroll 22. The first and second coaters are now in operation and the paperweb is receiving a single coat on both sides.

In order to illustrate the part of the control system in FIG. 2 that isan embodiment of the invention, suppose that the defect detector 12senses a defect in the paper web. The single pole-single throw solenoidoperated switch (defect detector) is energized and closed by the sensingof the defect. A voltage potential with respect to the common wire 34 isapplied to the motor 57 by the defect detector switch through the wires58 and 59. In defect detectors, activation occurs during the time thedefect is passing by the defect detector, and ceases once the defect haspassed. Therefore, the single pole-single throw switch is momentarily inthe closed position and returns to the open position once the defect haspassed the defect detector. The drum timer 46 and the contact strips arerotated by the motor 57 during the momentary activation of the defectdetector to a position where the brush 52 contacts the contact strip 47.Since the strip 47 is tied into the main wire 37 by the wire 6t),potential with respect to common wire 34 is applied to the motor 57 bythe wire 61. The pickup shoe 52. and the contact strip 47 form a holdingcircuit which keeps the timer motor 57 running after the defect detector12 has been deactivated by the passage of the defect. After apre-determined rotation of the drum timer 46, the contact strip 43contacts the pickup shoe 53. The voltage potential from main wire 37 isfed through wire 62 to the solenoid of the two-way spring return valve30 which moves to a position where the fiuid loaded side of the cylinder26 is exhausted. The spring return on the cylinder 26 moves theapplicator roll 16 away from the paper web It), thus ceasing the coatingapplication in the first coater. It is to be understood that the timeinterval between defect detection and applicator roll removal issubstantially equal to the time required for the defect to travel fromthe defect detector 12 to a position just prior to the applicator roll16. Once the drum timer 46 has rotated slightly further, contact strip49 contacts pickup shoe 54 and applies, through wire 63, a voltagepotential to the solenoid of the two-way spring return valve 31. Thevalve 31 is moved to exhaust position whereby the fluid side of thecylinder 27 is exhausted, moving the blade 18 away from the paper web.Once again, the passage of the defect through the paper machine is timedso that the blade is removed from the paper web prior to the passage ofthe defect under the blade edge. After the drum timer 46 has rotated acircumferential distance equal to the length of the contact strip 48,contact is broken with the pickup shoe 53. The solenoid of the two-wayspring return valve 31 is de-energized by the break and the valve 31 isreturned by spring action to a position where the fluid is fed into thecylinder 27, thus replacing the blade 18 against the paper web. Noticethat as the drum rotates, contact is broken between the contact strip 48and the pickup shoe 53 after the contact between strip 49 and shoe 54.Therefore, the solenoid of the two-way spring return valve 3! isde-energized after the two-way spring return valve 31 which returns theblade 18 to the paper web prior to the applicator roll 16. The reasonsbehind this procedure, as explained above, are to remove the possibilityof transferring excess coating to the paper web by applying coatingwithout metering.

After an additional pre-determined drum timer 46 rotation, pickup shoe55 is contacted by contact strip 50, applying to the two-Way springreturn valve 32 a potential through wire 64. The two-Way spring returnvalve 32 is activated, whereby the fluid loaded side of the cylinder 28is exhausted. The sprin action of the cylinder 28 forces the applicatorroll 22 away from the paper web. Slightly further rotation of the drumtimer 46 causes the two-way spring return valve 33 to lower the blade 24from the paper web through the contact of pickup shoe 56 and contactstrip 51. Notice that the contact strip 5i) will remain in contact withthe pickup shoe 55 longer than the contact strip 51 will remain incontact with pickup shoe 56. The second coater operation is thereforeexactly the same as the first coater operation, the only differencebeing that since the second coater is further away from the defectdetector than the first coater, the time interval between defectdetection and the time that the defect reaches the second coater islonger. The relative position of the contact strips on the drum timerfor the second coater are further away from the pickup shoe contactsthan those of the first coater which compensates for the longer timeinterval. Once the drum timer 46 has completed a revolution, pickup shoe52 breaks contact with the contact strip 47, and de-energizes the motor57 by removing the voltage applied through the line 61 to a pole of themotor 57.

It is worthwhile to point out that the timer circuit as described hereinis an illustrative example of a preferred embodiment and is not intendedto be limiting. It is preferred to synchronize the speed of the motor 57with the speed of the paper machine at the coater section. This could beaccomplished by using a synchronous motor 57 which is driven by agenerator (not shown) attached to and rotating with the drive (notshown) of the coater section. In addition, cam timers could besubstituted for the drum timer.

It is evident from the preceding discussion that a second defect that isdetected after the timer cycle has begun will not activate the controlcircuit. As a result, the applicator rolls and the blades will not bedropped during the passage of the second defect. For example, supposethat a defect is detected which in turn starts the timing cycle.Sometime during the timing cycle, a second defect is detected. It iseasily seen that the activation of the solenoid operated singlepole-single throw switch (representative of the defect detectoractivation) will not affect the action of the drum timer 46 andtherefore, the coater components will possibly be in operating positionwhen the second of the defects passes through the coaters. Thepossibility is increased when the number of controlled componentsincreases. To minimize this possibility, FIG. 3 is a modified version ofa timer circuit according to the invention in which the number ofcontrolled components is increased and the basic circuit of FIG. 2 hasbeen altered to reduce the possibility of paper web breaks resultingfrom the occurrence of closely spaced defects.

In FIG. 3, a first drum timer 66 and a second drum timer 67 are cascaded(in series) past the defect detector 12. Pickup shoes and contact stripshave been added which, for example, may be for a third and fourth bladecoater or other machine components for which control is desired. Voltagepotential is obtained across the main wire 68 and the common wire 69.Jumper wires 70 and 71 lead from the common wire 69 to one of the polesof the timer motors 72 and 73, respectively. Another jumper wire '74 isfed from the main wire 63 to the defect de tector 12. A cascade wire '75joins the contact strips of the first and second drum timers to thejumper wire 74. All of the contact strips of both drum timers 66, 67receive a common potential from the cascade wire 75. Upon the passage ofa defect, the single polesingle throw solenoid operated switch (defectdetector 12) is closed, thereby applying a potential with respect tocommon wire 69 to the first drum timer motor 72 through wire '76. Thetimer motor 72 is activated and rotates the first drum 66 sufficientlyto bring contact strip 77 into contact with pickup shoe 78. In thismanner, a potential is applied to the timer motor 72 through wire 79,thus holding the voltage potential from main wire 68 with respect tocommon Wire 69 across the timer motor 72. Therefore, the timer motor 72of the first drum timer 66 continues to run after the defect detector isdeactivated as was explained in connection with FIG. 2. As the drumrotates, it makes and breaks contact with the pickup shoe 80 and thecontact strip 81, the pickup shoe 82 and the contact strip 83, thepickup shoe 84 and the contact strip 85, and the pickup shoe 86 and thecontact strip 87 much as explained in the discussion of FIG. 2. Itshould be evident that during the revolution the applicator rolls andthe blades of the first two coaters as shown in FIG. 1 have beencontrolled and to repeat their exact operation would be repetitious andunnecessary. Notice that just prior to the completion of the revolutionof the first drum timer 66, pickup shoe 8% contacts strip 89, therebyapplying voltage potential to a pole of the second drum timer motor 73through wire 90. It can be seen that a potential is across the timermotor 73 of the second drum timer 67 and that upon a slight revolutionof the first drum timer 66, contact is broken between the pickup shoe 88and the contact strip 09, and the shoe 73 and the contact strip 77thereby removing the voltage through wire 90 and stopping the timermotor 72, respectively. No potential is now applied through wire 90 tothe pole of the timer motor '73. However, the potential initiallyapplied caused a rotation of the second drum timer 67 so that pickupshoe 91 made contact with contact strip 92. Contact strip 92 has asimilar voltage potential and is a similar holding circuit as employedin the first drum timer circuit of FIG. 3 and the drum timer circuit ofF16. 2. It follows that pickup shoe 93 and contact strip 9 1, pickupshoe 95 and contact strip 96, pickup shoe 97 and contact strip 98, andpickup shoe 99 and contact strip 100 follow a procedure similar to thepickup shoes and contact strips of the first drum timer 66. Although notshown in FIG. 3, it is evident that these contacts could control asimilar third and fourth knife coater and to repeat the exact operationwould also be repetitious and unnecessary. It should be obvious thatupon one revolution of the second drum timer 67, the holding actioncreated by the pickup shoe 91 and the contact strip 92 would cease, andthe timer motor 73 would be de-energized.

By cascading the drum timers 66, 67 as shown in FIG. 3, the time percycle of each drum timer has been halved with respect to a single drumtimer handling a like number of components, and therefore the frequencyat which defects can pass by the defect detector and still operably bedetected has been doubled.

Referring to FIGS. 1 and 4, the tension rolls and 21 are in most cases anecessary and important component of a coater control system designedaccording to this invention. The tension control roll 15 in the firstcoater is free to move in the directions indicated by the arrows.

A fluid cylinder (not shown) exerts a holding force to the left, asviewed, on the tension roll 15. The force exerted by the cylinder iscounteracted by the tension in the paper web which tends to force thetension roll 15 to the right, as viewed. When the forces exerted by thecylinder and paper web are properly balanced, the tension roll islocated in approximately the center of its travel. Obviously, since thecylinder exerts a constant holding force, an increase in the tension ofthe paper web will displace the tension roll to the right, while adecrease in the tension in the paper web will displace the tension rollto the left. The tension control roll 21 in the second coater issimilarly free to move in the directions indicated by the arrows. Afluid cylinder (not shown) exerts a constant exterior force on thetension roll 21 so that changes in paperweb tension result in similartension roll displacement, i.e., increases in paper web tension movesthe tension roll 21 to the left as viewed, and decreases in paper webtension moves the tension roll 21 to the right as viewed.

The displacement of the tension rolls 15 and 21 is transmitted to aposition transmitter (not shown) that sends a signal proportional to thedisplacement from a predetermined set point to the coater section speedcontroller. In operation, when the tension in the paper web changes, themovement of the tension rolls 15 and 21 is transmitted by the positiontransmitter to the speed controller which alters the coater speed thusholding the paper web tensions substantially constant.

In lighter weight paper webs, the tension control system described abovedoes not operate fast enough to overcome the sudden and drastic tensionchanges that result from the sudden. absence of coating caused by thecessation of coating during the passage of defects in the paper web.

Having now described the operation of a typical tension roll assemblyand explained the need for a supplemental tension control, refer to FIG.4 which is an enlarged fragmentary circuit diagram similar to thecircuit shown in FIG. 2 into which a tension control circuit has beenincorporated. The tension rolls are referenced 15 and 21 and correspondto those of FIG. 1. In this particular embodiment, the drum timer isbroadly indicated by the reference 101. The defect detector isreferenced by the number 12. The timer motor is referenced by the number102. The voltage potential is obtained from main wire 103 and commonwire 104. Notice that a jumper wire 105 provides, through the singlepole-single throw switch of the defect detector 12, and through aholding circuit formed from the pickup shoe 106 and the contact strip107 a voltage potential to the timer motor 102 with respect to thecommon wire 104. Common wire 104 and its voltage potential with respectto the main wire 103 is connected to the other pole of the timer motor102 through the wire 108. The drum timer 101 contains pickup shoes 109,110, 111, and 112 which contact as the drum timer 101 rotates thecontact strips 113, 114, 115, and 116 respectively, forming a controlcircuit similar to FIG. 2 and could control a set of blade coaters asexplained in connection with FIG. 2. A Wire 1 17 connects one end ofsolenoids 118 and 119 to the common wire 104-. The other ends of thesolenoids 118 and 119 are connected to the pickup shoes 120 and 121,respectively. The solenoids 118 and 119 are connected to energize thetwo-way valves 122 and 123, respectively. The solenoids 118, 119, arede-energized and therefore the two-way valves 122, 123 are in a positionwhere a supply of water under pressure contained within the pipe lines124 is prevented from entering the pipe lines 125 and 126. The pipelines 125 and 126 terminate in shower heads 127 and 128, respectively.Water is added to the paper web automatically when the coating operationceases during the passage of a defect by the activation of the solenoids122 and 123. Referring to the drum timer 101, notice that the pickupshoe 120 energizes the solenoid 118 after the drum timer rotates apredetermined distance by contacting the contact strip 129. In addition,the contact strip 129 and the contact strip 113 are equal incircumferential length. In this particular embodiment, the contact strip113 controls the time at which an applicator roll, similar to 16 in FIG.2, is removed from the paper web. Obviously, the shower head 127 isadding moisture to the paper web for approximately the same time thatthe moisture is removed from the paper web by the extraction of anapplicator roll.

The same general description holds for the pickup shoe 121 and thecontact strip 131. Notice that the same relative position is heldbetween the contact strip 131 and the contact strip 115 which in thisparticular embodiment would control an applicator roll of the secondcoater. Is is an essential feature that the shower begin substantiallyin unison with the cessation of the coating application by theapplicator roll.

The essential function of the supplemental tension control is toanticipate the paper web tension changes that occur during the removalof the applicator rolls 16 and 22, and to begin tension correctionimmediately. Another form of supplemental tension control is coupledwith the standard tension control system described in connection withthe tension control rolls 15 and 21 of FIG. 1. Referring to FIG. 4, thecircuit energizing the solenoids 118 and 119 of the two-way valves 122and 123, respectively, is modified to energize the speed controllers ofthe first coaters 11 and the second coater 20, respectively. The speedcontrollers are energized to alter the coater speed simultaneously withthe removal of the applicator rolls 16 and 22. Unlike conventionaltension control systems, the speed controllers are not activated bychanges in paper web tension but by the supplemental tension controlsystem during the removal of the applicator rolls 16 and 22. The speedcontroller is returned to the conventional tension control system whenthe applicator rolls 16 and 22 are replaced on the paper web.

Sometimes it is highly desirable to protect against the possibility ofdown-time that results from web defects made in the coater sections bythe coaters. This possibility can be overcome by placing defectdetectors between the coaters. FIG. 1 contains a second defect detector132 that is placed between the first coater 11, and the second coater20. Defects developed by the first coater 11 will energize the defectdetector 132, which in turn will energize a control circuit similar tothat shown in FIG. 2. In this particular system, each defect detectorwill be incorporated into a control circuit that contains a drum timerhaving only two sets of contact strips and shoes, one for the applicatorroll and one for the blade.

It is evident that many more modifications and alterations are possiblein this control system that are still within the scope of the invention.No description herein is meant to be limiting, but illustrative of anembodiment according to the present invention. For example, fullypneumatic or electronic control circuts could easily be substituted forthe electro-mechanical circuits shown.

I claim:

1. Apparatus of the type described comprising:

(a) Means for coating a moving fibrous web of indefinite length,

(b) said coating means contacting said web during coating thereof,

() means for monitoring said web for the detection of defects therein,

((1) said monitoring means being located upstream of said coating means,

(e) means for temporarily removing said coating means from contact withsaid web upon detection of a defect therein by said monitoring means,and

(f) means responsive to said monitoring means for adjusting the tensionof said web simultaneously with the removal of said coating means fromsaid web.

2. The apparatus of claim 1 wherein:

(a) Said adjusting means comprises means for adding moisture to said webat a point on said web adjacent said coating means simultaneously withthe removal of said coating means from contact with said web.

3. Apparatus of the type described comprising:

(a) Means for continuously coating a moving fibrous web of indefinitelength,

(b) means located upstream of said coating means for continuouslymonitoring said web for the presence of defects therein,

(c) means for interrupting coating of said web upon detection of adefect therein by said monitoring means, and

(d) means responsive to said monitoring means for automaticallyadjusting the tension of said web during said interruption of coating.

4. The apparatus of claim 3 wherein:

(a) Said adjusting means comprises means for applying moisture to saidweb at a point on said web adjacent said coating means upon saidinterruption of coating.

5. Apparatus for continuously coating a moving fibrous web of indefinitelength comprising:

(a) Means for continuously applying a layer of coating to said movingweb,

(b) means for continuously metering said layer of coating,

(c) said metering means being located downstream of said applying meansand in contact with said web,

(d) means for continuously monitoring said web for the presence ofdefects therein,

(e) said monitoring means being located upstream of said applying means,and

(f) means responsive to said monitoring means for:

(l) discontinuing coating application upon detection of a defect in saidweb prior to the passage of said defect past said coating applyingmeans,

(2) removing said coating metering means from contact with said websubsequent to discontinuation of coating application and prior to thepassage of said defect past said coating metering means,

(3) replacing said coating metering means into contact with said webafter passage of said defect past said coating metering means, and

(4) resuming coating application after replacement of said coatingmetering means into contact with said web.

6. The apparatus of claim 5 wherein:

(a) Means are provided responsive to said monitoring means for adjustingthe tension of said moving web simultaneous-1y with the interruption ofcoating application.

7. The apparatus of claim 5 wherein:

(a) Means are provided responsive to said monitoring means for addingmoisture to said web at a point on said web adjacent said coatingapplying means simultaneously with the interruption of coating ap'plication.

8. Apparatus of the type described comprising:

(a) Means for continuously monitoring a moving web of indefinite lengthfor the detection of defects therein,

(b) said monitoring means including a normally open solenoid operatedswitch adapted to close upon detection of a defect in said web,

(c) a motor controllable by said solenoid switch,

(d) a drum'timer adapted to be driven by said motor,

(e) said drum timer including a plurality of contact strips,

(f) a plurality of pickup shoes corresponding in number to said contactstrips and arranged for engagement with said strips upon operation ofsaid drum timer,

(g) an applicator roll normally in contact with said moving Web,

(h) a metering blade located adjacent said applicator roll and normallyin contact With said Web,

(i) pipelines terminating in shower heads located adjacent saidapplicator roll,

(j) means interconnecting said applicator roll and one of said pickupshoes for removing said applicator roll from contact with saidweb uponengagement of said one pickup shoe With one of said contact strips,

(k) means interconnecting said metering blade and a second pickup shoefor removing said metering blade from contact with said web uponengagement of said second pickup shoes with a second of said contactstrips,

(1) means interconnecting said pipelines With a third pickup shoe forcausing moisture to flow through 12 said pipelines upon engagement ofsaid third pickup shoe With a third contact strip, and (m) said firstand third contact strips being substantially equal in length and longerthan said second contact strip.

References Cited by the Examiner UNITED STATES PATENTS 2,293,690 8/1942Harrigan. 2,312,310 3/1943 Bradner et a1. 10047 2,563,213 8/1951 Coleman317142 2,655,620 10/1953 Coleman 317-123 2,827,873 3/1958 Thorn 118-73,079,889 3/1963 Jacobs et al. 118-8 3,082,735 3/1963 Vaccaro 1177 X3,128,207 4/ 1964 Schmitt.

FOREIGN PATENTS 637,177 5/1950 Great Britain. 144,015 2/ 1954 Sweden.

RICHARD D, NEVIUS, Primary Examiner,

1. APPARATUS OF THE TYPE DESCRIBED COMPRISING: (A) MEANS FOR COATING AMOVING FIBROUS WEB OF INDEFINITE LENGTH, (B) SAID COATING MEANSCONTACTING SAID WEB DURING COATING THEREOF, (C) MEANS FOR MONITORINGSAID WEB FOR THE DETECTION OF DEFECTS THEREIN, (D) SAID MONITORING MEANSBEING LOCATED UPSTREAM OF SAID COATING MEANS,